The Dosimetric Evaluation of An In-House Software Developed For Metal Artefact Reduction On Two Different Radiotherapy Treatment Planning Systems

Metal Artefact Reduction (MAR) is very important in terms of dose calculation in radiotherapy. It was aimed to develop an in-house MAR software as an alternative to commercial software programs and to examine its effectiveness by comparing it with the SMART-MAR software which was available commercially. A phantom containing metal with high atomic number was designed and computed tomography (CT) images of this phantom were taken (Without-MAR images). The obtained CT images were processed with the SMART-MAR software and the developed In-House MAR software. Processed images were compared in terms of Hounsfield unit (HU), absolute dose values ​​in the Accuray and CMS XiO treatment planning systems, and gamma evaluation. The best HU improvement was observed in the developed In-House MAR. The maximum mean percentage differences in absorbed doses at the determined points in Accuray was found 33.3% and 32.5% between Without MAR - SMART MAR and Without MAR- In-House MAR, respectively. The In-House MAR software developed by using MATLAB was shown similar results with the SMART MAR software. Although in-house MAR software needs to be investigated clinically, it is more advantageous than commercially available software in terms of being cost-free, applicability in a shorter time and without reconstruction.

Analysis of gamma index using in-house developed heterogeneous thorax phantom

Quality assurance (QA) before patient treatment plays a major role in complex radiotherapy (RT) treatment planning. Phantoms are the standard materials that are used for the pre-treatment QA of patients. Contemporary phantoms used in RT are mainly water-based, having simple geometry and of uniform density. These phantoms dose not replicate the exact heterogeneities of the actual human body. The present work aims to evaluate the results of relative dosimetry performed on in-house developed heterogeneous thorax phantom (HTP) using an electronic portal imaging device (EPID). To perform the relative dosimetry, contours were drawn on HTP at three different locations and intensity modulated radiotherapy (IMRT), as well as Rapid ARC (RA), were generated on it to compare the fluence obtained on TPS as well as on linac machine. The gamma evaluation results indicate a strong correlation between planned and the measured fluence. We found the EPID-based QA done on HTP explore its property as a QA tool and it can further be used to perform patient-specific relative dosimetry.

PSEUDO-3D IMRT VERIFICATION WITH EBT3 RADIOCHROMIC FILM

This work proposes a new method for pseudo-3D verification of intensity-modulated radiation therapy (IMRT) dose distributions. Unlike commercial solutions, it uses measured doses only for gamma evaluation. Its resolution is far better than with electronic detectors within the measured plane and comparable in other directions. It is readily available at clinics because it uses existing resources—a slab phantom and EBT3 films. The method was tested on six IMRT clinical cases. An in-house code for 2D and pseudo-3D gamma analysis was written in MATLAB and compared to OmniPro I’mRT.